1. Field of the Invention
The present invention relates to an image forming apparatus, and specifically relates to an apparatus for forming a full color image on a recording sheet by electrophotographic method.
2. Description of the Related Art
Generally, in full color copiers and printers using electrophotographic methods, four developing devices are provided which respectively accommodate cyan (C), magenta (M), yellow (Y), and black (Bk) toner corresponding to the three primary colors red (R), green (G), and blue (B), as well as black (Bk), wherein a toner image of each color is formed on the surface of a photosensitive member and transferred onto an intermediate transfer member in sequential primary transfers to form a four-color overlay, and the full color image comprising said four-color overlay is transferred onto a recording sheet at one time via a secondary transfer. Although a small type photosensitive member having a diameter of about 30 mm is usable, the intermediate transfer member must be of a size at least equal to the size of the largest recording sheet usable in a printer or the like. Accordingly, conventional intermediate transfer members are fixedly mounted in the apparatus, and cannot be replaced by a user. Certain disadvantages arise when the intermediate transfer member is fixedly mounted in the apparatus, including inconvenience during maintenance, and lack of assured space when removing paper jams and the like.
Consideration has been given to designs which allow the intermediate transfer member and photosensitive member to be removed from the apparatus body, but such removable construction requires elimination of the problems described below. First, toner leakage must be prevented from the residual toner cleaning means provided for the intermediate transfer member. Typically, such cleaning means is constructed so as to make pressing contact with the intermediate transfer member only during secondary transfers, and is separated from the intermediate transfer member at all other times. Thus, when the intermediate transfer member is removed from the apparatus body while the cleaning means is in the separated state with respect to said intermediate transfer member, toner may leak from the gap between the intermediate transfer member and the cleaning means. Then, the problem of protecting the exterior surfaces of the photosensitive member and intermediate transfer member must be addressed. When a hand inadvertently touches the photosensitive member or intermediate transfer member, oils adhere to the members and cause deterioration of image quality or said members are damaged by contact with foreign matter.